Dál gCais

The Dál gCais (also Dal Cais; IPA: [d̪ɑːɫ gaʃ]) were a dynastic group of related septs located in north Munster, and who rose to political prominence in the early medieval era in Ireland. They claimed descent from Cas mac Conall Echlúath (hence the term "Dál", meaning "portion" or "share" of Cas), though in later times for reasons of political expediency they claimed descent from the ancestor of the EóganachtaKings of Munster, Oilliol Olum.

In early historic Ireland they were an obscure group, one of many of the subject peoples of the Éoganacht. In the seventh and eighth centuries, when the overkingdom of Uí Fiachrach Aidhne fell into decline, they moved north and annexed Tuadh Mumhan (Thomond). Previously part of Connacht, it became part of Munster.

Thomond was to remain the heartland of the Dal gCais and its septs; it is most especially associated with the family of O'Brien (Ua Briain, Ó Briain), who reigned as its kings from the 930s to 1543, and from 1543 to the present day as Baron Inchiquin. The current incumbent (18th Baron Inchiquin) is Conor O'Brien; a thirty-second generation descendant of Brian Boru (High King of Ireland, 1002-1014. He is also known simply as The O'Brien, and is Chief of the Name, Prince of Thomond.